The term structure here is used to refer to a structural framework, for example made out of metal profiles or the continuous face of an interior or exterior wall, made for example of concrete, whether this wall is vertical, horizontal or inclined. This may for example be a separation wall, a supporting wall or a retaining wall for an embankment. The term structure also refers to structural framing elements in the roof of a building, whether the latter is meant for domestic—residential or commercial—professional use. The facing sheets in the known covering devices of this type are formed by panels or sheets made of rigid material, for example metal sheets, fastened to the structure. By way of a variant, they may be non-metallic panels, for example made of polymer material, whether or not transparent, or of composite material which will also be referred to as “sheets” in the following sections.
These sheets are generally rectangular in shape and are provided with at least two parallel ribs distributed on two parallel edges of the sheet. The ribs are adapted in order to either overlap, or be overlapped by a similar rib of another sheet, when the sheets are placed side by side or abutting one another. The partial overlapping of the sheets contributes to the sealing of the covering of the structure.
The fastening of the facing sheets in the structure is effected by means of screws or rivets driven into the constituent elements of the structure or the intermediate elements attached on to the structure, for example made of metal or wood, in order to provide for gaps interspersed in the thickness of the covered wall, for the purposes of insulation, air circulation or through passage of functional components, such as cables, for example. It is thus that in such a configuration, it is possible to either provide or not, a space between the sheets and the structure that allows, for example, for the introduction and placing of an insulating material and/or the through passage of pipes or cables.
Such fastening should as far as possible be air and water tight in order to ensure compliance with insulation performance requirements required by regulation. It is usually effected by drilling of the metal sheet during the riveting thereof or screwing thereof into the structure. As necessary, at each rivet or screw fastening a seal is provided so as to ensure the sealing tightness.
By way of an example that illustrates the above, the document EP-A-1 233 118 proposes the permanent fastening, on a structure constituted of a wall and profiled sections integrally attached to the wall, of rectangular sheets, by means of rivets.
Furthermore, during the construction, it is possible to provide for certain variations in the function and/or appearance of coverings thus produced. It is possible for example to alternate the zones/areas or sections of sheets with different colours or to interpose transparent zones therebetween in order to allow light to penetrate into the interior. It is also possible, to a certain extent and by making use of connection pieces or transitional profiles, to alternate zones in which the dimensions in width (between ribs) or in length are different. However, once the covering is in place, it remains there for periods that can be fairly long, often over several decades without it being possible for any substantial change in the appearance or functions thereof to be made at the risk of altering the structural integrity and protective qualities, in particular the sealing tightness or weather resistance thereof.
Thus it so happens that if users wish to place on the sides of the building, signage or warning signs, or even advertising hoardings or billboards, they are forced to drill new holes in the cladding sheet or sheets in order to effect the attachment of such signage paraphernalia as necessary. The same applies to the addition of functional elements, such as lighting points, cable trays or other members. These drilled holes contribute to degrading the integrity of the sheets in which they have been borne and affect their longevity and appearance over time. This deficiency is further compounded when the elements added are to be dismantled in order for them to be replaced by others that require drilling new holes.
Thus the existing systems are afflicted by a dual limitation or deficiency. On the one hand they do not allow for the possibility of easily implementing coverings with variations in appearance or multiple motifs or patterns in each surface covered, independently of the constraints imposed by the undiversified configuration of the sheets available and by the needs linked to their overlapping on the edge. On the other hand, they have very poor capacity to support the addition of detachable elements that are likely to be modified or moved one or more times during the useful life of the constructed structure covered.
In order to circumvent this problem, the prior art document EP-A-1 233 118, previously cited above proposes attaching on to the sheets mentioned here above, which are already fixed to the structure, cassettes that are only clip fastened onto the edges of the sheets, by snap action engagement of complementary forms. This solution, which requires drilling of the sheets only for their definitive attachment to the structure with the rivets and which therefore eliminates the need to drill the sheets in order to mount the cassettes, thus provides the ability to hide the rivets cited above. However, on account of the snap action connection, the overall strength and resilience and the stability of this solution remain limited, unless provisions are made for some expensive adjustments or modifications.